Electron beam rotation synchronizing circuit



5- Q A. M SKELLETT 1 2,337,045

ELECTRON BEAM ROTATION SYNCHRONIZING CIRCUIT Filed July 17, 1942 I 2 Sheets-Sheet 1 ans ramp 2/ FIG.

OU7PU7 E HANAEBS TO LINE WWWPL NO.2 I M/l/ENTOR AMSKELLETT b FIG. A By I: Z $74 127 0/ a2 I O I AT ORNZ-Ik Oct. 16, 1945.

A. M. SKELLETT 2,387,045 ELECTRON BEAM ROTATION SYNCHRONIZ'ING CIRCUIT 7 Filed July 17, 1942 2 Sheets-Sheet 2 FIG. 2

GAS 202 F/L0 /2/5 2/7 a 2/4 216' 12/3 M 2/8 i-2/2 20.?

AM SKELVLETT BVZW A T TORNE V Patented 15, ,15'

2,387,045 msc'raon Bung ROTATION srNomoNIz- Albert M. Skellett, Madison, N. a, assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 17, 1942, Serial measure 13 Claims. '(Cl. 178-531) This invention pertains to the automatic synchronization o! the rotation of electron beams in radial beam vacuum tubes, such as described in applicants prior Patent 2,213,774 issued October 15, 1940. More particularly, the invention pertains to the automatic synchronization of the rotation of electron beams in radial beam vacuum tubes used as transmitting and receiving distributors in multiplex transmission over long distances in communication systems.

Multianode radial beam tubes will find many more applications in the electrical industry ii The invention herein provides a rotating magnetic held for the electron beam in a multianode electron beamreceiving tube which field is in-- dependent of the local power supply at the receiving station. Multianode beam tubes so arranged are suitable for instance in telegraph systems where the start-stop distributor is now useofL' The invention may be understood from the following description when read with referenc to the associated drawings in which:

Fig. 1 is one embodiment of the invention which shows a multianode radial electron beam vacuum tube receiving circuit arranged to rotate an -electron beam in receiving tube l in synchronism with a rotating beam in a corresponding transmitting tube at a distant transmitting station (not shown) so that the beams rotate uniformly and engage corresponding anodes in each tube simultaneous-' ly. Tube 8 has twelve anodes. Two of the anodes, anodes 2 and 3, are used for synchronizing. The output circuits connected to the other ten anodes connect to ten work channels, lettered A to J, through transformers. The circuit employs six complementary tubes to eiiect synchronization.

Fig. 2 is a simplified embodiment of the invention. In Fig. 2 only two complementary tubes are required.

Fig. A shows the voltage graph for two relaxation oscillators forming part of Fig. 1.

Refer now to Fig. 1. Before the operation of the circuit per Fig. 1 is described in detail, the

It. is'an object oi the invention herein to pro-' vide instrumentalities for. use in radial beam tubes in multiplex communication circuits for starting and maintaining their electron beams in synchronism even though they may be separated bygreat distances and supplied with independent sources of power not in synchronism at the transmitting and receiving station.

In certain multiplex circuits. presently known which use radial electron beam vacuum tubes it is not possible to send current of the frequency to produce the revolving fields required for rotating the beam over one of the channels intercom nesting the transmitter and receiver since the fundamental frequency of the pulses is considerably higher thanflthat of the current supplied to the stators for revolving the beam. conceivably,

. one might feed the pulses from. a pilot channel into a subharmonic generator and from this.

derive the correct frequency for the stators but this method would present some problems of starting. To start a system utilizing the circuit described herein it is only necessary to turn on the pilot channel signals at the transmitter and the-electron beam at the receiver will immediately start to rotate in exact synchronism with that at the transmitter, that is to 'say, the system becomes immediately operative.

manner in which it functions will be described in a general way to facilitate the understanding of the detailed description to follow.

In the system to be described the line t is assumed to be incoming from a distant transmitting station (not shown) where it is connected to a radial electron beam multianode transmitting tube having twelve anodes and corresponding generally to receiving tube l. Two of the anodes in the distant transmitting tube correspond to anodes 2 and 3 of receiving tube 5 and serve as synchronizing anodes. The anodes of multianode beam tubes are maintained at a positive potential relative to the oathode.- When the grid is made positive relative to the cathode a stream of electrons is emitted from the cathode and flows toward a particular anode. The direction in which the' streamof electrons flows is controlled by a magnetic field which pervades the space insldethe envelope of the tube. in the present invention the stator of a fi-phase motor surrounds the glass envelope-of multianode radial beam tube l. The direction of the electron stream depends upon the magnetic steady potentials from a loca1' power source to the input circuits of tubes 4 and 5. When signals are being received over the line the inputs of tubes 4 and are, in eifect, transferred so that they are responsive to the signals incoming over the line from the transmitter.

The distant transmitting tube is arranged in a manner well known in .the art so that the first stream of electrons which its cathode emits, as the stream is simultaneously established and started to rotate, is directed at an anode in the distant transmitting tube in a position corresponding to the position of anode 2 in receiving tube I.

The circuit of the invention herein is arranged so that when no signals are being received from the transmitting tube and while the receiving tube i is awaiting the first signal pulse over the line 9 from the distant transmitter, steady currents are supplied from the outputs of tubes 4 and 5 to their respective coils in the stator surrounding tube I. The relative magnitude of the-output current of tubes 4 and 5 is such that the fields which are established by the stator coils tend to direct any electrons emitted by the cathode toward anode 2.

While no signals are being received by tube I from the distant transmitter there is no electron beam in. tube I. There are, however, magnetic fields set up in the stator coils surrounding the glass envelope of tube I tending to direct any electrons which maybe emitted by the cathode of tube I toward anode 2.

Thus, the first signal received over the line 9 will be as a result of the direction of a stream of electrons in the transmitting tube in the distant station at an anode in a position corresponding to the position of anode 2 in r'eceiving'tube I. A stream of electrons will\be emitted from cathode I2 in response to the reception of the first signal. Theefiect of the preestablished magnetic field will direct the beam instantly atanode 2.

The impinging of the first stream of electrons on anode 2 will result, in a manner to be described, in the starting of the generation'of two saw-tooth shaped voltage waves. The period of the waves and their relation to each other is controlled, once they are started, by the impinging of beams on-anodes 2 and 3. The waves are maintained in quadrature. They are translated into substantially sinusoidal voltage waves in quadrature which are impressed by vacuum tubes 4 and, 5 on their respective stator coils surrounding tube 1. This will rotate the beam in tube I in substantial synchronism with the rotation of the beam in the distant transmitting tube. Any slight difference in the speeds of r'otationof the two beams will be corrected once per revolution in a manner to be described so that once started the receiving tube beam is maintained in synchronis'm with the beam ofthe transmitting tube. Furthermore, the beam in the receiving tube I is directed at a particular anode in tube I simultaneously with the direction of the beam in the distant transmitting tube at a corresponding anode in the distant tube.

voltage pulse from the distant station, the gen'- anode 2. The steady output irom each of tubes 4 and 5 necessary to direct the first beam at anode 2 is obtained by impressing a steady potential between the grid and cathode of each of Simultaneously with the reception of the first 1 pulse from the distant transmitter by receiving tu e I and in response to its reception, the character of the output of tubes 4 and 5 is changed in a manner who described so that these tubes deliver substantially sinusoidal voltages in quadrature to the? stator coils. The period of oscillation of the sinusoidal voltages impressed on the stator coils of tube I while signals are being re-' ceived from the transmitter is maintained the same as the period of rotation oi'the electron beam in the transmitting tube at the distant station. I

The circuit of Fig. 1 features two relaxation oscillators which generate two saw-toothed voltage waves in quadrature. These two voltage waves are indicated by the curves in Fig. A. When the first stream of electrons impinges on anode 2 in response to the'receptlon of the-first eration of the saw-toothed voltage wave byv one of the relaxation oscillators is inaugurated. When the stream oi electrons impinges on anode 3 of It hasbeen pointed out above and it is em- &

phasized that during the waiting period before signals are received over the line from the trans-' mitting station by tube I, asteady current is supplied from' tubes 4 and 5 to the coils of the stator; surrounding thev envelope of tube I so as to gentube I which is separated from anode-2 by 90 degrees, a. saw-toothed voltage wave generated by the second relaxation oscillator in Fig. 1 is inaugurated. The saw-toothed voltage wave generated by one relaxation oscillator is impressed on the inputof tube 4 which responds by delivering a substantially sinusoidal wave to its respective stator-coil in its output circuit. The second sawtoothed voltage wave generated by the second relaxation oscillator in Fig. 1 is impressed on the input of-tube 5 which respondsby delivering a substantially sinusoidal voltage wave in quadrature with that delivered by tube 4 to its Esme-s tive stator coils in the output circuit of tube 5.

As long as the beam in tube I continues to tate, the relaxation oscillators controlled by anodes 2 and 2 will continue to generate their saw-toothed voltage waves. This in turn willresult in the continued generation of the substantiallv sinusoidal voltage waves in quadrature by oscillators 4 and 5. On the instant that the reception of voltage impulses from line .9 connecting receiving tube I to the distant transmitter ceases, the generation of the saw-toothed wave by the relaxation oscillators will also cease responsively. Steady potentials will again be impressed instantly on the inputso! tubes 4 and I by their respective potentiometers. A steady magnetic field tending to direct-electrons toward anode 2 will be set up in the stator coils surrounding the envelope of tube I so that the tube will be in condition to start.

The circuit per Fig. 1 will now be described-in detail. When the system oi. Fig. 1 is in condition to receive signals, but before signals are actually received, the circuit of Fig. 1 sets upa magnetic field in the stator coils surrounding the envelope erate a steady magnetic field which tends to direct a stream of electrons it generated toward of'multianode beam tube I such that any electrons-which may be emitted from the cathode I2 in response to the reception of a signal will be aaeaoes directed toward anode 2. Thi is achieved as a result of. current flowing in the output circuit of Coil trigger tubes i5 and i6 and secondary emission 2 tubes 34 and 35 described in my copending application Serial No. 321,852, filed March 2, 1940, are deactivated. Steady potentials are impressed betweenthe grid and cathode of tubes 6 and 5 by potentiometers connected to their input cir-. cuits to maintain the grid of each at the proper negative potential with respect-to its cathode so as to provide steady outputs from tubes d and 5'.- .This is effected by means of an individual potentiometer associated with the input circuit of tubes 4 and 5. The potentiometer circuit for tube 3 may be traced from ground through positive battery l9, resistance 20, resistance 2|, resistance 22, negative battery 23 and back to ground. The grid of tube 4 is connected through coil 50 to the junction between resistances 2| and 22. The potentiometer circuit for tube 5 may be traced from ground through positive battery 26,

resistance 25,'resistance 26, resistance 27, negative battery 28 and back to ground. The grid of tube 5 is connected through coil 5! to the Junetion'between resistances and 21. The output circuitfor tube 4 may be traced from positive battery 38 through stator coils 29, shunting condenser 52, and through the primary of transformer I and coil 30 to the anode of vacuum tube 4 and to its cathode to ground. The output circuitfor tube 5 may be traced frompositive battery 3| through statorcoils 32, shunting condenser 53, and through the primary of transformer I! and coil 33 to the anode of vacuum tube 5 and to its cathode to ground. A steady current flows in the output circuit of each tube. relative magnitudes of the currents are maintained by a proper choiceof circuit constants so that the fields set up by these stator coils tend to direct the first electron beam emitted by cathode i2 toward anode 2. H

A circuit may be traced from positive battery 6 through the upper portion of the winding of the secondary of transformer 1. through the primary of transformer 8 to anode.2 of multianode beam tube 5. The potential of grid H 01 tube l is nor-' mally negative with respect to cathodel2 due to negative battery 13 which is connected from the grounded cathode i2 through resistance id to grid H. The conductor 9 is connected at its disv tant end to a multianode beam vacuum tube transmitter arranged with twelve anodes and having two anodes corresponding to anodes 2 and 3 arranged as synchronizing and starting anodes. The circuit extends through condenser ill to the junction between grid H and the upper terminal of resistance Id.

with res ect to its cathode i2.

trons will be emitted from cathode l2 and, as a result of the efiect of the stator magnetic held, it will be directed at anode 2,

Attention is called to the condensers 39 andflfl. Condenser 39 is connected between the junction In response to an incoming signal the grid H is made momentarily positive A stream of elec- The 6i oi potentiometerresistances 20 and 2t and ground. The anodes oi tubes ifi'a'nd 3d are also connected through resistances t0 and at, respectively, to junction ti. Condenser is connected between junction 62 of potentiometer resistances 25 and. 2b and ground. The anodes oi tubes it and 35 are also connected through resistances 8i and 5?, respectively, to junction G2.

I The constants of the elements of the potentiometer circuits are chosen so that while no signals are being received by tube i the poten tial across condenser 39 is indicated in Fig. A by the ordinate 0a. The potential across condenser so for the same condition is indicated in Fig. A by the ordinate ab. These potentials are applied between the anode and cathodes of trigger tubes l5 and it, respectively.

In response to the directing of the first electron beam at anode 2, a current pulse will flow through the ,primary of transformer d. A voltage pulse will be generated in the primary and induced and inverted in the secondary windings of the transformer. As a result of the positive voltage pulse in the top secondary winding of transformer 8 tube i5 is fired instantly. The firing point is indicated at point Pi on the curve phase 9 in Fig. A. I

Negative battery 45 is normally connected be tween ground and the grids of tubes 3% and 35 through the bottom secondary winding of trans: former 8, rectifier $3 and resistances El and M,

to maintain tubes 36 and 35 deactivated.

.The positive voltage induced in the .bottom sec-.-

ondary winding of transformer 8 is applied through rectifier 33, across condenser M and through resistances Q1 and 58 between the grids and cathodes of Both tube 34 and tube 35 are activated instantly.

Condenser M is charged to a relatively high potential by the effect of the current flowing in secondary emission tubes wand response to the single voltage surge through the about the same potential .as their cathodes.

On each negative half-cycle condenser it starts to discharge through rectifier 43 in the high resistance direction. The discharge is relatively slow. Before it can discharg sufficiently, as a result'of the rotation of the beam in a manner to be described, the beam in tube willbe Dositioned so that it again impinges onanode 2 andv condenser 84 will be recharged. In other words once rotation is started condenser M will receive relatively heavy surges of charging current once per rotation of the beam in tube I and condenser 66 will be discharged so slowly between charging intervals that tubes 5M and 35 will remain acti-' vated as long as the beam rotates. It is pointed out that the manner in which the sinusoidal voltages in quadrature are generated to rotate the beam will become apparent from the following.

Attention is es ecially directed to'the fact that tubes 36 and 35 are activated simultaneously. Both-tube 3d and tube 35 are activated in response to the impingin of the first stream of electrons on anode 2 in tube 0 and the response is instantaneous. r

To return now to a consideration of the effect of the firing of tube I 5. Tube I5 fired instantly in response to the impinging of the first stream of electrons on anode 2 in tube I. When tube I5 fires it provides a discharge path through the tube for condenser 39. As condenser 39 discharges through tube I5 its potential decreases from the indicated by ordinate on, as shown by ;he curve phase I in Fig. A, until it reaches 1 point at which tube I5 is deactivated. From ;his point the potential across condenser 39 in,- zreases due to the effect of the current flowing n theoutput circuit of tube 34, which as has been :xplained, remains conducting. LCI'OSS condenser 39 rises again to a peak equal to ts original potential a as indicated by the curve ahase I. Then tube I is refired by the effect if a. stream of electrons impinging on anode 2 a econd time dueto the rotation of the electron learn in a manner to be explained.

Refer now to the curve marked phase 2 in Fig. l. lenser 40 before thefirst signal impulse is reeived from the distant station is indicated by rdinate ob. It was also explained that tube 35 was activated simultaneously with the activation 1' tube 34 at the instant the first electron beam npinged-on anode 2 intube I. Condenser 40 connected in the output circuit of tube 35. The istant tube 35 is activated the potential across ondenser 40 starts. to rise as indicated by the urve phase 2 in Fig. A. The potential across tie condenser will continue to rise until tube I6 fired in response to th impinging of the elecron beam on anode 3 in tube I as the beam is atated. i

When the electron beam in tube I impinges on node 3, as the, beam is rotated, current will flow .orn positive battery 6 through the bottom poron of the secondary of transformer ll, through 1e primary of transformer I8, to anode 3 of tube through the space separating the anode 3 and ithode I2 of tube l and to ground. A voltage ulse will be generated in the primary of transrmer 53 which will be induced and inverted in ie secondary of transformer 18 to fire tube I5 hich is normally deactivated by the effect of agative battery BI connected between-its ground- I cathode and grid. Tube is will fire at point P2 on the curve phase in Fig. A. After the tube fires the condenser I will discharge through the tube. The patcha'l across condenser '30 will decline as indicated ong the line P2622 until a point'is reached at hich the tube I 6 is deactivated, when it will rain rise due to the efifect of the chargin curnt in the output circuit of tube 35. The potential across condenser 39 between notion 4| and'ground will be applied between a grounded cathode and grid of tube 4 through sistance 2i and coil 50. The potential across ndenser 40 will be applied between the groundcathode and grid of tube 5 through resistance and coil 5]. The slopes of the curves phase and phase 2 can be controlled by a proper nice of the constants of the elements comprisg their circuits. In response to the impressing of the saw-tooth ltage wave of the curve phase I on the input tube 4, a sinusoidal voltage wave is generated the output circuit of tube 4 which isapplied the stator coils 29. In response to the imessing of the saw-tooth voltage wave of the we phase 2 on the input or tube 5, a sinusoidal ltage wave is generated in the output c cu t The potential As explained above, the potential across conof tube 5 which is applied to stator coils 32. As shown in Fig- A the' two saw-toothed voltages are displaced in phase. The first peak 01 the curve of phase I, as has been shown, occurs at the in- I? stant when the electron beam in tube I impinges on anode 4.. The corresponding first peak of the sinusoidal voltage wave impressed on stator coils 29 will occur 'at the same instant. The generation of the sinusoidal voltage wave in tube 5 will 10 start at the same instant that the beam in anode I impinges on anode 2, as the voltage across condenser 40 is raised above the normal voltage at which it is maintained during the interval before the reception of the first signal impulse by tube I. Thus in response to the reception of the first signal impulse by tube I and the impinging of the first electron beam on the anode 2 of tube I, two difierent voltage waves are instantlyi-mpressed on the input of tubes 4 and 5. The respective magnitudes of the two voltage waves impressed on the inputs of tubes 4 and 5 are controlled by a choice of circuit constants so that, in response thereto, the outputs of tubes 4 and 5, when impressed on their respective stator coils 29 and 32, rotate the electron beam in tube I so that when it impinges on anode 3, separated from anode 2 by 90 degrees, during the first revolution it will receive a synchronizing pulse which has been directed at an anode in'a corresponding position in 30 the transmitting tube at the distant station.

This synchronizing pulse will fire tube E6. The

time of occurrence and voltage across the condenser 40 "at the instant is indicated by the time and voltage ordinates of the point P2 in Fig, A, at which point in voltage and time tube I5 fires. This point marks the maximum voltage attained by condenser 40. Its magnitude is controlled so that it is equal to voltage 0a. The time i trolled so that it is separated from Pl by one quarter of ajull voltage change cycle.

a After tube It fires, the voltageacross condenser '38 will decline as indicated in Fig. A by the line P2Q2. Tube I6 is deactivated at point Q2. :Then

If the voltage across condenser 40. will again rise as indicatedby the curve phase 2 in Fig. A due to the charging of condenser II) by the output'of tube 35.

Each time the beam in tube I is rotated it will receive one synchronizing impulse from the transmitting tube .en it impinges on anode 2 and a second synchronizing impulse from the transmitting tube when it impinges on anode 3. Trigger tube I5 will bealternately activated during the first half of its cycle while .condenser 39 discharges through it and inactivated during the succeeding half cycle while the voltage across condenser 39 rises. During a cycle displaced by 90 electrical degrees, trigger tube It will be alter nately activated during the firsthalf of its cycle while condenser 46 discharges through it and inactivated during its succeeding half cycle while the voltage across condenser 40 rises.

The net result is, as indicated by the curves phase I and phase 2 in Fig. A, the generation of two saw-toothed voltage waves displaced with respect to each other by 90 electrical degrees, with the period of each wave controlled by its corresponding synchronizing pulse in the distant transmitter. Any tendency of either wave to depart from synchronism is corrected once per cycle.

The two saw-toothed voltage waves in quadrature are applied to the inputs of tubes 4 and 5 which in response thereto generate two sinusoidal voltage waves in quadrature which are applied to their respective statorcoils to rotate the beam in tube 2 in synchronism with the rotating beam in the transmitting tube.

The translation of the saw-toothed waves into waves which are substantially sinusoidal is achieved by the filtering action of the tube circuits. It depends upon-two factors: 1, negative resistance furnished by the tube in the regener-- ,ative circuit and, 2, the turning of the stator coils in the plate circuit to resonance at the cyclic frequency of the waves. action is adjusted so that the negative resistance introduced is less than the positive resistance of the tuned circuit, that is, just under the condition of oscillations.

Coils 55 are connected in series to battery 56. There is one coil 55 for each coil 29 and 32. Their windings are arranged so that they neutralize the effect of the direct current component in the output of vacuum tubes 4 and 5.

When the rotation of the electron beam in the distant transmitting tube stops, synchronizing pulses will no longer be received. Condenser d4 1 will have time to discharge.

'will be deactivated by negative battery 45 con- Tubes 34 and 35 nected to their grids. The potentiometers connected to tubes d-and 5 will impress the proper potentials on the input circuits of tubes d and 5 so that the magnetic field developed by the stators in their output circuits will again tend to direct electrons emitted in response to the first signal pulse received by tube toward anode 2. The potentials impressed across condensers 39 and .60 under control of their individual potentiometer circuits will again be as indicated by the ordinates a and ob and the circuit will be 'again in.

condition to start.

It is necessary to suppress one of the electron beams, as two electron beams separated by 180 degrees tend to be emitted by the cathode. The

is connected at the distant transmitting station as tube 20! and generally corresponding thereto.

The regenerative manner in which this is performed is described in A. M. Skellett Patent 2,217,774 of October 14,

The two phase anode supply required for suppressing one of the two electron beams is obtained from transformers I and I! in the anode circuits of tubes 4 and 5. The secondaries of these transformers are also shown as connected to anodes 2 and 3. The positive battery between the center taps of these secondaries and ground is sufilcient to make anodes 2 and 3 operative with no alternating current flowing, that is atthe time of starting and the alternating current is of sufficient magnitude to neutralize this battery for the unwanted beam. At the start both beams, spaced 180 degrees apart, will therefore,

be operative and a false signal in the anode diametrically across from anodes 'willbe produced by the starting function. This false signal which is limited to a single pulse in the anode circuit directly opposite anode 2 should not cause any serious inconvenience for most applications.

Refer now to Fig. 2 which shows a simplified receiving circuit arranged to rotate an electron beam in synchronism with the rotation ofa beam in a transmitting tube at a, transmitting station. The circuit per Fig. 2 employs only two complementary tubes instead of six as in Fig. 1. The

two complementary tubes in Fig. 2 are arranged in push-pull relation. 'lhe circuit results in the supplying of two substantially sinusoidal voltage waves in quadrature to the stator coils.

In Fig; 2 tube 25H is a multianode radial electron beam vacuum tube. Tubes 202 and 203 are each gas-filled trigger tubes. The conductor 20% the same potential as that of parallel.

the cathodes of tubes Z02 and203, arranged in parallel, through positive battery 2H5 and resistance 2!! to the mid-point oi the primary of transformer 2E8 from which parallel branches extend through the upper and lower portions of the primary winding of the transformer to the anodes of tubes 202 and 203 in parallel. Condenser M5 is connected between the anodes of tubes 202 and 203. A circuit may be traced irom the bottom terminal of the secondary of transformer US through stator windings are which are connected in parallel with stator winding 220 and condenser ZZI and the circuit returns over a common branch to the top terminal of the seconuary of the transrormer :18.

The circuit of condenser Z and the primary of transrormer'zw is tuned to resonateat the cyclic Irequency of rotatlonof the beams which may be or the order of on cycles.

when tube runs awaiting a pulse there is no field in the stator coils surrounding the envelope or tube m. Tubes :02 and Zoe, which are gasfilled trigger tubes, are deactivated. 'When a signal impulse is received over the line, grid 20:! is made more positive with respect to its cathode 206. Electrons will be emitted from cathode 206 and some of them will be attracted to anode 2|0.

A negative. pulse will be impressed across the primary or transiormer Zl-i. The pulse will be induced and inverted in the secondary of transformer 2 l3.

The output circuit of tubes 202 and 203 is arranged in a manner well known in the art as a parallel inverter. Condenser 2l5 serves as a commutator to deactivate one tube in response to the activation of the other by impressing a negative potential on the anode of one in response to the activation of the other. This will be described herein briefly.

It will be assumed that the voltage of battery M6 is volts. While tubes 202 and 203 are deactivated the anode of each tube and each terminal of condenser 265 will be at substantially e right-hand or polstitive terminal of battery 2 H5 or at positive 115 vo s. v

In response to the first pulse one or the other of tubes 202 or 203 will fire depending upon which is faster or on the circuit constants. The other tube will remain deactivated for the first half of the cycle. It will be assumed that tube 202 fires. Current will flow from the right-hand terminal of battery 216 through resistance 2!? and upwardly through the top portion of the primary of transformer 218, through tube 202 from anode to cathode and back to the left-hand or negative denser 2I5 will be changed to positive -15 volts.

The potential of the anode of tube 203 and the bottom terminal of condenser 2l5 will drop to positive volts, which is so low that tube 283 will. not be fired immediately thereafter by effect. of the same pulse which fired tube 202. The time constants of the circuits must be adjusted so that the voltage of the anode of tube 203 will rise at least to a potential high enough to permit it to be tired by the effector the succeeding impulse impressed through transformer 213 between the grid and cathode of thetube 203.

When the beam in tube'20l is rotated, inn manner to be described, so that it impinges on anode 2, tube 203 will be activated. Thepotential of the anode of terminal of condenser tube 203 and the bottom 2|5 will be changed from plus 115 volts to plus 15 volts, a reduction of 100' volts, and the potential of the top terminal of condenser 2l5 will be correspondingly reduced for a transient interval, until equilibrium is restored, to negative 85 volts. I This will extinguish tube 202.

Current will flow from battery MB through resistance 2, bottom portion of the primary of transformer 2l8, from the anode to the cathode of tube 203 and back to thenegative terminal of battery 2l6.

Tubes 202 and 283 will be and deactivated on each half cycle in response to the synchronizing pulses received each half cycle by tube Although the grids of tubes connected in parallel and bothreceive impulses whenever a. beam impinges on either anode m or 2!! which are also connected in parallel, the impulse on only one of the grids will be effective after either tube has been fired, because the other tube is fired and in this co dition its grid has no control. 4 i 1 The voltage induced in the secondary of trans- 282 and 203 are the alternately activated in response to the of signals from said circuit, toward a particular preselected one of said-anodes in said tube.

2. In a communication receiving circuit a multianode radial beam vacuum signal receiving tube, a cathode in said tube, a plurality of anodes in said. tube, an electron beam direction control connected to said tube, and means in said direction control for tending to direct electrons, to be emitted in response to the reception of the first of a train of signals by said tube, toward a particular anode, during the interval while no sigable electron beam I tube having a plural former 218 will be reversed each half cycle under :ontrol of the incoming pulses from line 204. Soils 219 connected in parallel with coils 22b and :ondenser 22i arranged in series generate sub- ;tantially sinusoidal voltage waves in quadrature n response to these reversals.

The beam in tube 2IJ| is rotated in response to he rotation of the magnetic fields produced by he coils in response to the incoming signals. Any endency to var'y from synchronism with the Ieam in the transmitting tube will be corrected aeh time a beam impinges on anodes 2H] and l The circuit per Fig. 2 is suitable for radial beam ibes having an odd number of anodes or an ven number of anodes since two pulses per cycle 31 the control of the gas-filled trigger tubes may e obtained with either arrangement.

For teletypewriter use, in place of the usual Jtary start-type distributor well-known'in the alegraph art a twelve-anode radial beam tube ould be suitable. The tube would be arranged that both beams were operative and opposite nodes would be connected together. This would ve five channels for the teletypewriter code and ie for synchronism.

What is claimed'is:

1. A multianode radial beam vacuum signal :ceiving tube, an incomingcommunication ciriit connected thereto, a cathode in said tube, a urality-of anodes, spacedeach from the other, pl; of said anodes arranged to engage a rotat- 118 electron beam in said tube and means nnected to said tube for directing said electron am when emitted by said cathode in said tube plurality of anodes,

' input circuit, of the nals are beingreceived by said tube.

- 3. In an electrical circuit a multianode radial electron beam vacuum tube, an electron beam directing device associated with said tube, a plurality of controls connected to said device, means responsive to one of said controls operating to tend to direct an. electron beam toward a. particular anode in said tube and means responsive to another of said controls for rotating an electron beam in said tube.

4. n multianode radial electron beam vacuum tube, an input circuit connected to said tube, a spaced each from the other, arranged to engage a rotatin said tube and means responsiveto the reception in said tube, from said first of' a. train of signals, for directing said electron beamtoward a particular preselected anode in said tube.

5. The method of operating an electron beam number of anodes with establishing an electron each of said anodes associated means for beam in thetube and beam which comprises establishing electrical conditions, when no electron beamis directed to an electron beam to while maintaining said conditions, electron beam directed to said anode.

6. In ;.a,multianocle electron beam receiving tube, the method of controlling an electron beam in said tube which comprises generating, through the output circuit of said tube, a saw-toothed voltage wave, each voltage impulse of which wave has a slope the reverse of the preceding voltage impulse and causing the period of said wave to be controlled by incomin'g signals.

7. In a. multianode electron beam receiving creating an tube the method of controlling the rotation of an electron beam in said tube which comprises as steps: (1) the generation of a saw-toothed. voltage 'wave having a period controlled by incoming signals, (2) the translation of said sawtoothed wave into a substantially sinusoidal wave, and (3) applying the efiect 01' said sinusoidal wave to the rotation of said beam.

8. In a ,multianode electron beam receiving tube the method of controlling the rotation of an electron beam in said tube which comprises as steps: (1) the generation of magnetic fieldsv tending to direct an electron 'beam ata particular' anode while no signals are being received, (2) the generation of a rotating field having a period of rotation controlled by incoming signals reception of the first or a. train I means for controlling the ase'aoae radial beam tube, a plurality of anodes in said tube connected to a plurality of relaxation oscillators means for controlling the start of operation of said oscillators by the impinging of an electron beam on a particular anode in said tube and means responsive to said start of operation for controlling the phase relationship of the voltages generated by said oscillators to control the movement of said beam.

11. In a rotating electron beam synchronizing device for a multianode receiving tube in a communication system, a beam directing device, means for supplying current of uniform magnitude to said device while said tube is awaiting the reception of signals, means responsive to said current of uniform magnitude for establishing a condition within said tube, tending to direct an electron beam emitted by said tube in response to the reception of the first signal element of a train of signal elements by said tube, first at a particular preselected one of a plurality of anodes in said tube, means responsive to the reception of said first signal element for directing said beam at said preselected anode and means responsive to the reception of said first signal element for changing said current to a variable current to rotate said beam.

12. In a synchronizing device for a rotating alectron beam in a multianode radial electron beam tube in a communication signal receiving circuit, means for charging a condenser in response to the impinging of an electron beam on a particular anode, means for controlling the rate of discharge of said condenser, a radial electron beam directing device and means responsive to voltage variations of said condenser for controlling said directing device.

13. In a communication system, a multianode radial electron beam receiving tube arranged to receive signals from a corresponding transmitting tube and means comprising a parallel inverter connected between .the outputof said receiving tube and a beam rotating device for said tube for synchronizing the rotation of the electron beams in each tube.

ALBERT M. SKELLE'IT. 

